> You'd be talking 1970s or before, then? Anything from the 80s onwards has had plenty of electronics present.
No, it's completely different in the last ~decade.
Certainly cars back into the 80s (some brands into the 70s) have electronics but they are completely independent and simple systems. You had individual wiring to every device and for the most part (usually 100%) independent circuits for every component.
This makes things very easy to diagnose with just a volt meter, easy to replace and even easy to completely rip out some subcomponent if you didn't care for it (or it became too expensive to repair). All the rest of the car was independent of that one component so everything keeps working.
This simple contruction is true into the 00s for most brands/models.
Current cars have integrated everything into a common bus and everything is controlled and monitored by opaque software that can't be diagnosed or fixed outside of factory tools.
For example even something as trivial as replacing the starting battery on newer BMWs (possibly other brands) requires special electronic tooling to reprogram the computer. That's just the tip of the iceberg, nearly nothing can be done in newer cars without access to factory electronic tools since everything is interconnected and hidden behind proprietary software control.
I have cars from the 80s, 90s and mid-00s and all of them require nothing more than a voltmeter to diagnose electrical problems. That's no longer true with new cars.
> modern ones are much more reliable and need less servicing
That's mostly true. But once they do require servicing, it's becoming nearly impossible to DIY so you are at the mercy of how long the factory cares to support your model.
I used to own a mid-00s (so not even that complex by current comparison) BMW and electrical glitches from the interconnected fragile electrical system were common. Even though I normally do everything in all my cars, there was nothing I could do without access to factory diagnostic tools so had to take it to the shop. Eventually the technicians there basically gave up, diagnosing things was so difficult that even with all the factory tooling they estimated tens of thousands in labor just to figure out the problems. I had to sell the car for scrap value since it was unfixable.
Give me simple cars from the 80s and 90s, I can keep those running forever myself.